U.S. patent number 6,164,782 [Application Number 08/760,130] was granted by the patent office on 2000-12-26 for self-contained lighted marking device.
This patent grant is currently assigned to 3M Innovative Property Company. Invention is credited to Stephen J. Pojar.
United States Patent |
6,164,782 |
Pojar |
December 26, 2000 |
**Please see images for:
( Certificate of Correction ) ** |
Self-contained lighted marking device
Abstract
A self-contained lighted marking device that is a directionally
dependent line light source has a substantially transparent
housing. The housing has a narrow cross-section, preferably
rectangular in shape. A thin, flexible film having a smooth surface
on one side and a plurality of linear substantially right angled
isosceles prisms on the other side is located along the periphery
of the interior of the housing. A light source, preferably a
plurality of light emitting diodes, are located at at least one end
of the housing.
Inventors: |
Pojar; Stephen J. (Scandia,
MN) |
Assignee: |
3M Innovative Property Company
(St. Paul, MN)
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Family
ID: |
23233836 |
Appl.
No.: |
08/760,130 |
Filed: |
December 3, 1996 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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317477 |
Oct 4, 1994 |
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Current U.S.
Class: |
359/528; 359/527;
362/183; 362/339; 362/243; 359/530; 359/529 |
Current CPC
Class: |
F21V
5/02 (20130101); F21V 7/00 (20130101); F21V
5/002 (20130101); G02B 5/045 (20130101); G02B
6/0096 (20130101); F21W 2111/00 (20130101); F21Y
2115/10 (20160801); F21V 2200/40 (20150115); F21W
2111/02 (20130101); F21S 9/02 (20130101) |
Current International
Class: |
F21V
8/00 (20060101); F21V 7/00 (20060101); F21V
5/02 (20060101); G02B 5/04 (20060101); F21V
5/00 (20060101); F21S 8/00 (20060101); F21K
7/00 (20060101); F21S 9/02 (20060101); F21S
9/00 (20060101); G02B 005/12 () |
Field of
Search: |
;359/527,528,529,530,532,538,551 ;362/243,183,339,340,276
;385/133 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 290 267 A2 |
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Nov 1988 |
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EP |
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0 292 159 |
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Nov 1988 |
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EP |
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89 09 067 U |
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Jan 1990 |
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DE |
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4-110988 |
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Apr 1992 |
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JP |
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WO94/06051 |
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Mar 1994 |
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WO |
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Primary Examiner: Spyrou; Cassandra
Assistant Examiner: Sikder; Mohammad Y.
Attorney, Agent or Firm: Buckingham; Stephen W.
Parent Case Text
This application is a continuation of Ser. No. 08/317,477 filed
Oct. 4, 1994, abandoned.
Claims
What is claimed is:
1. A self-contained lighted marking apparatus comprising:
a substantially transparent housing having a longitudinal axis
running from a first end of said housing to a second end of said
housing, said housing having a narrow cross-section, one dimension
of said cross-section being greater than a second dimension;
a plurality of light emitting diodes for providing light within
said housing, said plurality of light emitting diodes located at
said first end of said housing;
means for providing power for said plurality of light emitting
diodes; and
a thin, flexible film substantially located along inner periphery
of said housing, said film having a totally internally reflected
smooth surface on one side of the film and a plurality of linear
substantially right angled isosceles prisms forming a plurality of
peaks and grooves on another side of the film, each of said grooves
of said prisms having an axis, said axes of said prisms running
parallel to said longitudinal axis of said housing.
2. The self-contained lighted marking apparatus according to claim
1, further comprising a second plurality of light emitting diodes
for providing light within said housing, said second plurality of
light emitting diodes located at said second end of said
housing.
3. The self-contained lighted marking apparatus according to claim
1, wherein said light emitting diodes are strobed at a high
rate.
4. The self-contained lighted marking apparatus according to claim
1, wherein said light emitting diodes are positioned to provide
light at an angle to said axes of said prisms of said film.
5. The self-contained lighted marking apparatus according to claim
4, wherein said angle is between 5 and 20 degrees.
6. The self-contained lighted marking apparatus according to claim
1, further comprising reflecting means located at said first and
second ends of said housing for reflecting incident light within
said housing.
7. The self-contained lighted marking apparatus according to claim
1, wherein said means for providing power comprises a photovoltaic
cell for producing voltages when exposed to radiant energy.
8. The self-contained lighted marking apparatus according to claim
7, further comprising storage means for storing energy generated
from said photovoltaic cell and for providing power for said light
emitting diodes.
9. The self-contained lighted marking apparatus according to claim
1, wherein said film has an oval cross-sectional shape.
10. The self-contained lighted marking apparatus according to claim
1, wherein said film has a teardrop cross-sectional shape.
11. A self-contained lighted marking apparatus comprising:
a substantially transparent housing having a longitudinal axis
running from a first end of said housing to a second end of said
housing, said housing having a narrow substantially rectangular
cross-section and a first face and a second face;
a plurality of light emitting diodes for providing light within
said housing, said plurality of light emitting diodes located at
said first end of said housing;
means for providing power for said plurality of light emitting
diodes;
a light extractor for directing light out of said first face of
said housing, said light extractor having a first smooth side and a
second structured side, said second structured side having a
plurality of linear prisms thereon facing the interior of the
housing, each of said prisms having first and second sides; and
a thin, flexible film substantially located along inner periphery
of said second face of said housing, said film having a smooth
surface on one side of the film and a plurality of linear
substantially right angled isosceles prisms on another side of the
film, each of said prisms having an axis, said axes of said prisms
running parallel to said longitudinal axis of said housing.
12. The self-contained lighted marking apparatus according to claim
11, wherein said first and second side of each said prisms of said
light extractor make an angle in the range of 59 to 79 degrees with
one another.
13. The self-contained lighted marking apparatus according to claim
11, wherein said marking apparatus further comprises
retroreflective sheeting on the outside of said first face of said
housing.
14. The self-contained lighted marking apparatus according to claim
11, wherein said light emitting diodes are angled at said film.
15. The self-contained lighted marking apparatus according to claim
11, further comprising switching means for selectively providing
power to said light source.
16. A self-contained lighted marking apparatus having a first color
on first portions and a second color on second portion, said
marking apparatus comprising:
a substantially transparent housing having a longitudinal axis
running from a first end of said housing to a second end of said
housing, said housing having a narrow substantially rectangular
cross-section and a first outer face and a second outer face;
a light source for providing light within said housing, said light
source located at said first end of said housing;
a light extractor for directing light out of said first outer face
of said housing, said light extractor having a first smooth side
and a second structured side, said second structured side having a
plurality of linear prisms thereon facing the interior of the
housing, each of said prisms having first and second sides;
a thin, flexible film substantially located along interior
periphery of said second outer face of said housing, said film,
having a smooth surface on one side of the film and a plurality of
linear right isosceles prisms on another side of the film, each of
said prisms having an axis, said axes of said prisms running
parallel to said longitudinal axis of said housing;
retroreflective sheeting having a first face and a second face,
said second face of said retroreflective sheeting adjacent said
first face of said housing;
coloring means for providing said first color at said first
portions of said marking apparatus, said coloring means adjacent
said first face of said retroreflective sheeting at said first
portions; and
means for providing said second color, said means for providing
said second color being adjacent said second face of said
retroreflective sheeting at said second portions of said marking
apparatus.
17. The self-contained lighted marking apparatus according to claim
16, further comprising reflective sheeting having a first face and
a second face, said first face of said reflective sheeting adjacent
said means for providing said second color and said second face of
said reflective sheeting adjacent said first outer face of said
housing.
18. A self-contained lighted marking apparatus having a first color
on first portions and a second color on second portion, said
marking apparatus comprising:
a substantially transparent housing having a longitudinal axis
running from a first end of said housing to a second end of said
housing, said housing having a narrow substantially rectangular
cross-section and a first outer face and a second outer face;
a light source for providing light within said housing, said light
source located at said first end of said housing;
a light extractor for directing light out of said first outer face
of said housing, said light extractor having a first smooth side
and a second structured side, said second structured side having a
plurality of linear prisms thereon facing the interior of the
housing, each of said prisms having first and second sides;
a thin, flexible film substantially located along interior
periphery of said second outer face of said housing, said film
having a smooth surface on one side of the film and a plurality of
linear right isosceles prisms on another side of the film, each of
said prisms having an axis, said axes of said prisms running
parallel to said longitudinal axis of said housing;
retroreflective sheeting having a first face and a second face,
said second face of said retroreflective sheeting adjacent said
first face of said housing;
coloring means for providing said first color, said coloring means
adjacent said first face of said retroreflective sheeting at said
first portions; and
means for providing said second color, said means for providing
said second color being adjacent said coloring means at said second
portions of said marking apparatus.
19. The self-contained lighted marking apparatus according to claim
18, wherein said means for providing said second color comprises
opaque retroreflective sheeting.
20. A self-contained lighted marking apparatus comprising:
a substantially transparent housing having a longitudinal axis
running from a first end of said housing to a second end of said
housing, said housing having a narrow cross-section;
a light source for providing light within said housing, said light
source located at said first end of said housing;
a thin, flexible film substantially located along inner periphery
of said housing, said film having a totally internally reflected
smooth surface on one side of the film and, a plurality of linear
substantially right angled isosceles prisms forming a plurality of
peaks and grooves on another side of the film, each of said grooves
of said prisms having an axis, said axes of said prisms running
parallel to said longitudinal axis of said housing; and reflecting
means located at said first and second ends of said housing for
reflecting incident light within said housing.
Description
FIELD OF THE INVENTION
The present invention generally relates to the field of marking
apparatuses, such as for use with traffic lanes. In particular, the
invention is directed to a self-contained lighted marking device
that is a directionally dependent line light source.
BACKGROUND OF THE INVENTION
Traffic lanes are delineated by using pavement markings,
retroreflective markers, point source lamps, and recently, lighted
guidance tubes. Painted pavement markings are often difficult for
drivers to see at night, so retroreflective markers have been
developed to improve the ability of the drivers to locate and see
the markers. While retroreflective markers retroreflect incident
light, they do not provide any illumination. For some applications,
such as marking railroad crossings or construction work zones,
illumination is desirable, possibly used in conjunction with
retroreflective markings, to increase the ability of drivers to see
the marked area. For example, gate arms, particularly at railroad
crossings, are marked with diagonal stripes, typically alternating
red and white. The stripes are painted or are retroreflective
sheeting. Red steady burn or flashing lights often accompany the
gate arms. Construction barricades also typically are marked with
diagonal stripes. Red or orange lights are often mounted on top of
the barricades. The lights mounted on top typically have a life of
ten to twenty days, depending on the time of year, and for flashing
lights, two to three months. The lights usually run on two six-volt
lantern batteries.
Illumination, in the form of lighted guidance tubes, has also been
used to mark roadways. Lighted guidance tubes utilize a thin,
flexible film made of a transparent polymeric material having a
structured surface and a smooth surface, wherein light striking
either surface is totally internally reflected. An example of this
type of film is described in commonly-assigned U.S. Pat. No.
4,906,070 to Cobb, Jr. An example of a lighted guidance tube is
described in commonly-assigned U.S. Pat. No. 4,805,984 to Cobb, Jr.
For lighted guidance tubes, a circular cross-sectional shape is
used for superior light transport characteristics, to allow maximum
distance between light sources. Because of the desire to illuminate
as great a length as possible, highly collimated halogen light
sources are usually used. These light sources, however, have low
efficiency and a short life span. It is often preferable to use the
lighted guidance tubes for poorly lit roadways, to ensure the
driver can adequately follow the roadways. Often, however, it is
difficult or uneconomical to provide electrical power for the light
sources in the lighted guidance tubes in remote areas or where only
a short delineation system is required.
SUMMARY OF THE INVENTION
To overcome the limitations in the prior art described above, and
to overcome other limitations that will become apparent upon
reading and understanding the present specification, the present
invention provides a self-contained lighted marking device that is
a directionally dependent light source. The self-contained lighted
marking device has a substantially transparent housing having a
narrow cross-section, preferably rectangular. Inside the housing, a
thin, flexible film having a smooth surface on one side and a
plurality of linear substantially right angled isosceles prisms on
the other side is placed substantially along the periphery of the
interior of the housing. A light source is placed at the end of the
end of the housing. Preferably, the light source comprises a
plurality of light emitting diodes.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more fully described with reference
to the accompanying drawings wherein like reference numerals
identify corresponding components, and:
FIG. 1 is a side cross-sectional view of the present invention
configured for guidance applications;
FIGS. 1a and 1b are side cross-sectional views showing alternative
configurations of optical film for guidance applications;
FIG. 2 is a perspective view of a roadway with the present
invention installed on the roadside;
FIG. 3 is a perspective view of a railroad crossing;
FIG. 4 is a side cross-sectional view of the present invention
configured for marking applications;
FIGS. 4a and 4b are blown-up cross-sectional views of two
alternative embodiments of a portion of the face of the embodiment
shown in FIG. 4; and
FIG. 5 shows the present invention configured as a railroad gate
arm and further shows the angles light is emitted from the front
and back faces of the gate arm.
FIG. 6 shows a perspective view of the present invention showing
light source at both ends of the lighted marking device.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
To overcome the limitations in the prior art described above, and
to overcome other limitations that will become apparent upon
reading and understanding the present specification, the present
invention provides a self-contained lighted marking device. The
marking device may be used for traffic lane delineation, for
marking obstacles, such as barricades or gate arms, to increase the
conspicuousness of vehicles as well as decorative accent lighting.
Referring to FIG. 1, a cross-sectional view of a first embodiment
of the present invention is shown. The first embodiment is
particularly useful for guidance-type applications, as light is
directed at shallow angles out of the device, as will later be
described. Guidance device 10 has substantially transparent outer
housing 12, preferably made of polycarbonate, although any rigid,
substantially transparent material may be used. Outer housing 12 is
tubular in form and preferably has a rectangular cross-sectional
shape. The cross-sectional shape, however, may be any
cross-sectional shape having a relatively narrow cross-section.
Optical film 14, with a microstructured surface, is placed
substantially along the inner periphery of outer housing 12.
Optical film 14 is a thin, flexible film made of a transparent
polymeric material having a structured surface and a smooth
surface, wherein light striking the smooth surface is totally
internally reflected. The structured surface is preferably a linear
array of substantially right angled isosceles prisms forming a
plurality of peaks and grooves. A preferred film is described in
commonly assigned U.S. Pat. No. 4,906,070 to Cobb, Jr. which is
hereby incorporated by reference. Optical film 14 is placed within
outer housing 12 such that the grooves run parallel to the
longitudinal axis of outer housing 12. The structured surface of
optical film 14 is the outer surface of the tubular optical
film.
Totally internally reflecting films have been used in tubular forms
with a circular cross-sectional shape to take advantage of their
superior light transport characteristics, to allow maximum
distances between light sources. In guidance device 10, however, it
is often preferable to use shorter sections of housing. With a
shorter section of housing, the goal is not transporting light over
long distances, but rather to emit more light from guidance device
10. Therefore, outer housing 12 has a narrow cross-section to
increase the number of reflections light rays make with optical
film 14. With a rectangular cross-section, as shown in FIG. 1,
optical film 14 may be placed within outer housing in a number of
ways. For example, as shown in FIG. 1, optical film 14 may lie
substantially along the longer wall of the rectangular cross
section and curve to the opposite long wall near each of the
shorter walls of the housing. FIG. 1a shows another possible
placement of optical film 14 substantially along the interior of
outer housing 12, where optical film 14 has a teardrop shaped
cross-section. FIG. 1b shows yet another possible cross-sectional
shape of optical film 14, an oval. Further, the cross-sectional
shape of optical film 14 further is dictated by the properties of
optical film 14. Those skilled in the art will readily recognize
that numerous shapes and combinations of shapes exist for outer
housing 12 and optical film 14 to increase the number of
reflections light rays make within guidance device 10 for the
purposes of the present invention.
A light source is located at one end of guidance device 10 to
provide illumination to the device. For lighted guidance tubes,
highly collimated halogen light sources are often used to
illuminate as great a length of tube as possible. The highly
collimated halogen light sources, however, have low efficiency and
a short life. For applications where illuminated guidance devices
are placed in remote locations, it is desirable to use light
sources and power sources that do not need to be replaced very
frequently. Therefore, a light source having high efficiency and
long life is needed. Referring back to FIG. 1, a plurality of light
emitting diodes (LEDs) 16 are placed at the end of guidance device
10 to provide illumination. LEDs 16 are preferably angled at
optical film 14 to increase the number of reflections by optical
film 14 over the number that would occur if light rays from LEDs 16
were substantially parallel to the longitudinal axis of outer
housing 12. While the positioning angle of LEDs 16 varies with the
length of guidance device 10 and the beam spread of LEDs 16, a
preferred range of angles is between five and twenty degrees.
Because some light escapes from guidance device 10 at each
reflection, increasing the number of reflections allows shorter
sections of guidance device 10 to use less intense light sources
and still appear as bright as longer guidance devices lit with high
intensity lamps. LEDs 16 are further preferable as light sources
for the present invention because of their high efficiency and long
life. For example, if 30 milliwatt LEDs are used, approximately 8
to 16 LEDs, depending on the illumination desired, are preferably
used to illuminate a six meter length of guidance device 10. LEDs
have a life on the order of 50-100,000 hours, thereby eliminating
of the need to replace the light source frequently. Further, in
another embodiment of the present invention, LEDs 16 may be strobed
at a high rate, for example, 50 to 1000 times per second, thereby
conserving battery life without causing any perceivable
flicker.
To further increase the number of reflections within guidance
device 10 and thereby increase its illumination, reflective
sheeting 18 is placed on both inside ends of outer housing 12 to
reflect light back down inside the optical film 14. Preferably, 3M
brand Silverlux, manufactured by Minnesota Mining and Manufacturing
Company, St. Paul, Minn., an opaque reflective sheeting, is used
for reflecting the light. As shown in FIG. 6, at the other end of
guidance device 10, another set of LEDs 16 may be used such that
light is provided from both ends of guidance device 10.
Alternatively, only reflective sheeting is used.
In lighted idance tube applications, power is typically provided to
the lighted guidance tubes by means of electrical wiring, which
causes problems when the lighted guidance tubes are installed in
remote areas or only short delineation systems are required.
Therefore, to provide power for the light source, battery 19 may be
included within guidance device 10 to make guidance device 10
completely self-contained. Battery 19 is preferably a long life
alkaline battery, although any battery may be used. A preferred
alkaline battery provides several weeks of continuous operation.
Photovoltaic cell 20 may also be included to recharge battery 19,
such as a nickel cadmium or other rechargeable battery, when cell
20 is exposed to radiant energy. Photovoltaic cell 20 in
combination with a rechargeable battery can provide substantially
unlimited continuous operation in sunny environments.
FIG. 2 is a perspective view of a roadway having guidance device 10
installed on the roadside. Guidance device 10 is particularly
useful to delineate the side of the road, as shown in FIG. 2,
traffic lanes or other obstacles that vehicles may encounter along
the roadway. Guidance device 10 is a directionally dependent line
light source, emitting light at shallow angles, preferably on the
order of zero to twenty degrees from the longitudinal axis of
guidance device 10, with virtually no light emitted at near
perpendicular angles. Therefore, motorists travelling on roadways
delineated with guidance devices will see distant sections of the
guidance devices that the motorists are approaching while sections
of the guidance devices near and to the side of the motorists will
become dim and hardly visible. This minimizes distraction and glare
from the side. Conversely, non-directional light sources, such as
fluorescent tubes, used in this type of application appear
brightest to the side of the motorist, increasing glare and
distraction. Thus, guidance device 10 only directs light to where
it needs to be seen, specifically, toward drivers of vehicles on
the roadway.
Referring to FIG. 3, a railroad crossing is shown. Railroad
crossings are typically marked with signs 42, gate arms 40, marked
with diagonal stripes, alternating red and white, and steady
burning lights 44. Signs 42 typically are painted, or more
preferably, have retroreflective sheeting on their face to improve
their visibility to drivers at night. Lights 44 caution drivers as
well as provide illumination to further alert drivers that an
obstacle is present in the roadway. White stripes 46 are also
typically white retroreflective sheeting to define the general
length of the gate arm at night.
FIG. 4 shows a cross-sectional view of the present invention when
used for marking applications. Outer housing 51 of marking device
50 is tubular in form and preferably has a rectangular
cross-section, although any narrow cross-sectional shape may be
used. Outer housing 51 is substantially transparent and is
preferably made of polycarbonate. Housing 21 has a first face 55
and a second face 53. Light extractor film 52 has a smooth surface
and a structured surface, the structured surface having a plurality
of linear prisms facing the interior second face 53 of outer
housing 51. In a preferred embodiment, the prisms of light
extractor film 52 form isosceles triangles having an angle of
69.degree.. This angle is selected because it causes light
traveling at an angle of 15.degree. to the longitudinal axis of
outer housing 51 to be emitted in a direction normal to that axis
and through face 64. Those skilled in the art will readily
recognize, however, that the exact angle of the isosceles triangles
may vary without significantly affecting the light extraction
performance of light extractor film 52, depending on a variety of
variables, such as the position of the light source, its
characteristics and the index of refraction of the extractor film.
Therefore, a preferred range of angles for the isosceles triangles
of light extractor film 52 ranges between 59.degree. and
79.degree.. Moreover, triangles other than isosceles triangles may
be used to extract light. Light extractor film 52 is placed along
the front inner face of outer housing 51 such that light striking
light extractor film 52 exits perpendicular the longitudinal axis
of outer housing 51, as opposed to the shallow angles of guidance
device 10 as shown in FIG. 1.
Optical film 54, a microstructured film that totally internally
reflects light, is placed behind right angle film 52. A preferred
optical film is described in the aforementioned U.S. Pat. No.
4,906,070 to Cobb Jr. Light is provided by light source 56,
preferably a plurality of light emitting diodes (LEDs). LEDs are
preferred because of their low power consumption, high efficiency
and long life. Light source 56 may be powered by battery 58,
photovoltaic cell 60 or a combination thereof. Light source 56 is
angled with respect to the longitudinal axis of outer housing such
that light rays from light source 56 will approach light extractor
film 52 at an angle between 1 and 40 degrees and preferably between
7 and 20 degrees. Optical film 54 transports light from light
source 56 along the length of outer housing 51 while light
extractor film 52 directs it perpendicularly out the front face of
outer housing 51. Because light is extracted from marking device
50, there is not as much light for optical film 54 to transport.
Therefore, it is preferable to include LEDs at both ends of marking
device 50. Also, reflective sheeting 62, such as 3M brand
Silverlux, may be placed at the ends of marking device 50 to
reflect light back within outer housing 51 that has not yet been
extracted by light extractor film 52. Marking device 50 is
particularly useful for marking applications where the potential
viewer will approach marking device 50 in a direction perpendicular
to the length of marking device 50. When the potential viewer
approaches from such a direction, light from marking device 50 will
be directed at the viewer.
Referring to FIG. 4a, face 64 will be described in more detail.
FIG. 4a shows a cross sectional view of a portion of face 64. Face
64 may be included in marking device 50 to give marking device 50
an efficient light distribution system as well as an aesthetic
appearance similar to traditional marking devices. Face 64
substantially consists of translucent retroreflective sheeting 70,
such as Scotchlite Reflective Sheeting Diamond Grade Series 3970,
manufactured by Minnesota Mining and Manufacturing Company, St.
Paul, Minn. Retroreflective sheeting 70 provides nighttime
visibility by redirecting light from the headlights of a vehicle
back to the motorist. Because the retroreflective sheeting 70 is
also translucent, light extractor film 52 directs light through
retroreflective sheeting 70 towards the motorist. Motorists in an
approaching vehicle can see the transmitted light before the
vehicle is close enough for retroreflection of the vehicle's
headlights, or when dew, frost, fog, or other environmental
conditions interferes with the retroreflection light path. Further,
in applications where selective illumination is desired, such as a
railroad gate arm marking device 50 may be controlled by switch 74,
such as a mercury switch, such that marking device 50 only
illuminates when the gate is lowered.
Railroad gate arms or construction barriers, often have striped
faces, for example, alternating diagonal red and white stripes, as
shown in FIG. 3. In such an embodiment, red LEDs may be used to
provide the color for the red stripes. Colored layer 72 is placed
in front of retroreflective sheeting 70 to give face 64 a colored
appearance. Colored layer 72 consists of a durable, transparent,
colored film, such as Scotchlite Electronic Cuttable Overlay Film
Series 1170, manufactured by Minnesota Mining and Manufacturing
Company, St. Paul, Minn. Colored layer 72 can also be a silk-screen
printed transparent ink. For example, to give face 64 a red and
white striped appearance, red stripes of colored layer 72 would be
added to the retroreflective sheeting, and would transmit the red
LED light. The white areas, however, would also transmit the red
LED light. Transmission of red light through areas desired to be
white may be prevented in different ways. A first method is to
include two additional layers between retroreflective sheeting 70
and outer housing 51 of marking device 50 as shown in FIG. 4a.
Reflective sheeting 66 reflects red LED light back into outer
housing 51, and white, electronically cuttable, durable, vinyl film
68, such as Scotchcal series 7725 ElectroCut Film, manufactured by
Minnesota Mining and Manufacturing, St. Paul, Minn., to give
daytime whiteness to the white segments of face 64. At night,
however, face 64 will appear red and black when internally
illuminated, and red and white when light is retroreflected off
retroreflective sheeting 70.
Referring to FIG. 4b, an alternate embodiment of face 64 is shown
for preventing transmission of red light through areas desired to
be white. In FIG. 4b, colored layer 72 is placed over the entire
face of retroreflective sheeting 70. An opaque retroreflective
sheeting layer 73 is placed over colored layer 72. Opaque
retroreflective sheeting 73 will retroreflect light, thereby giving
it a white appearance. At night, similar to the first method, face
64 will appear red and black when internally illuminated, and red
and white when light is retroreflected off opaque reflective
sheeting 73. This method simplifies assembly of face 64 by
eliminating the need for careful alignment of the different layers.
Yet another method of providing a striped appearance would be to
use white LEDs in FIG. 4a and exclude the additional reflective
sheeting 66 and vinyl film 68. Using such a method, the entire face
would be translucent, allowing multi-colored faced to be
illuminated.
FIG. 5 shows marking device 50 configured as a railroad gate arm
and shows an additional benefit of the embodiment shown in FIG. 4.
Light extractor film 52 directs light rays 80 perpendicularly out
of the face of marking device 50 and at incoming drivers. Referring
back to FIGS. 1 and 4, optical film 54 of parking device 50 directs
light similarly to optical film 14 of guidance device 10. Thus,
light rays 82 from the other side of marking device 50, are emitted
at shallow angles and are directed at oncoming trains. Therefore,
marking device 50 not only provides an illuminated barrier to alert
vehicles of an oncoming train, it also provides an illuminated
barrier to oncoming trains to assist them in locating the crossing
area at night.
Although a preferred embodiment has been illustrated and described
for the present invention, it will be appreciated by those of
ordinary skill in the art that any method or apparatus which is
calculated to achieve this same purpose may be substituted for the
specific configurations and steps shown. This application is
intended to cover any adaptations or variations of the present
invention. Therefore, it is manifestly intended that this invention
be limited only by the appended claims and the equivalents
thereof.
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